Method of treating metal parts



Patented July 12, 1938 UNITED STATES METHOD OF TREATING METAL PARTSCarroll C. Swift, Belmont, Mass, assignor to.

United-Carr Fastener Corporation, Cambridge, Mass., a corporation ofMassachusetts No Drawing. Application January 23, 1935,

Serial No. 3,199

3 Claims.

My invention aims to provide improvements in the method of treatingmetal parts during the preparation for finishing.- In the process ofmanufacture of small metal parts such as drawings 5 and stampings, it isnecessary to lubricate the stock as it is fed into the machines.Naturally a certain amount of the lubricant remains on the parts whenthey emerge from the machine in the finished state. This lubricant,which is often lard oil, or some special compound of petroleum, must becleaned from the parts before they can be plated or lacquered. The mostadvantageous time'to clean the parts is directly after they leave themachine.

One of the best known and most efficient cleaning methods is to wash theparts in trichlorethylene, a solvent of organic composition which ismarketed under a variety of trade names. I have found thattrichlorethylene is such an eflicient solvent that metal parts,especially those made of steel, are so clean that they begin to rust orcorrode immediately the solvent dries and they are exposed to atmosphereof more than usual humidity. Obviously this is an undesirable result ofany cleaning process, for in certain i'n-- dustries there-is often arather lengthy period between the cleaning and plating or lacqueringprocesses.

I It is the object of my invention to provide a process whereby themetal may be degreased and protected from rust at the same time..Obviously the solvent or degreaser must be used whatever the process,and I have therefore started with the cleaner as a foundation. The bestmethod of.

as preventing rust or corrosion of metal is to cover it with aprotective film of some moisture resisting material. In the case ofsmall parts, the film must be tough and durable as well asmoisture-resisting, since it must undergo severe treat- 40 ment inhandling and shipping. I have found that certain resins and oils,soluble in the organic solvents will dry evenly and quickly on the metalas soon as the solvent has evaporated, thereby forming a thin rust-prooffilm. While there are several available resins which are wholly orpartially soluble in t'richlorethylene, I prefer to use common rosin,both because of its low price and because of the ease with which it maybe dissolved in the degreasing solvent. Fur- 50 thermore, I have foundthat although many resins appear to be completely dissolved in tri.chlorethylene they forin small globules on the metal as soon as thesolvent has evaporated instead of forming a covering film. Rosin, on the55 other hand, invariably dries and her-dens in a smooth even film. Sucha film may be obtained by dissolving in trichlorethylene from two tofour ounces of rosin per gallon of solvent.

In order to provide a tougher and more durable film, I add to thedissolved rosin a certain amount of a vegetable oil such as boiledlinseed oil.

The linseed oil adds elasticity to the film and prevents the rosin fromdrying out and becoming brittle. A solution may be made at roomtemperature and used with great success without heating. I have found itadvisable to use three tanks of solvent, to be used in series. The lastone contains the rosin and linseed oil, while the first two insure athorough cleaning.

The filmobtained by my novel process may be used as a priming coat forsubsequently applied baked finishes, or it may be cleaned oil in the hotcaustic solutions which are normally used just prior to lacquering orplating.

It is to be understood that my method of cleaning and protecting metalis not exclusively useful for small metal parts, but is adapted topreserving unfinished metal in other forms as well.

I have found that resin and linseed oil, either separately or together,leave a very uniform film over the partwhen dil P and dried. The solventdries out rapidly and the resultant film does not pull together intoislands or bunches. However, a film of rosin alone deteriorates rapidlywhen exposed to air and becomes crumbly, porous, powdery and brittle.The addition of linseed oil strengthens the film, makes itnonhygroscopic, prevents oxidation of the film, keeps the filmtransparent and makes the film permanent, all without deleteriouseffect.

If too much boiled linseed oil is used, the resultant filmdoes notdryvery quickly and, therefore, I have found the best formula to containabout 1 gallon trichlorethylene, 4.5 ounces rosin by weight and 1 ounceboiled linseed oil by weight. Heavier concentrations can be used, butthe ratio of rosin to oil should be about 4 to 1 for best results.

While I have described a articular combination of materials by the useof which myinvention may be carried out, I do not wish to be limited bysuch description, as the scope of my invention is best defined by thefollowing claims.

I claim:

l. The method of cleaning and protecting metal which comprisessubjecting the metal to be cleaned to a solution containing rosin,vegetable oil and trichlorethylene and subsequently allowing thetrlchlorethylene to evaporate thereby leaving a protective coating ofthe rosin and oil on the metal.

2. The method of cleaning and protecting metal which comprisessubjecting the metal to be cleaned to a solution containing parts ofrosin and linseed oil in trichlorethylene and subsequently allowing thetrichlorethylene to evaporate thereby leaving a protective coating ofthe rosin and oil on the metal.

3. The method of cleaning and protecting metal which comprisessubjecting the metal to be cleaned to a solution containing about 97.5%trichlorethylene, about 2% rosin and about .5%

boiled linseed oil by weight and subsequently 5 allowing thetrichlorethylene to evaporate and leave a protective moisture-proofcoating of rosin and oil on the metal.

CARROLL C. SWIFT.

